Belts which have high tensile strength and have been used to date usually as, inter alia, drive belts or conveyor belts, contain a sheet as a tension layer, which is surrounded on both sides by a fabric provided with an adhesion promoter layer, each having a rubber friction layer arranged thereon. The fabric performs the function of mechanical stabilization of the tension layer and is an important connecting element for the rubber friction layer and the tension layer. In some cases, such belts transmit or absorb large forces, and the bonds between the individual layers therefore have to meet high requirements. A disadvantage of these belts is that fabric layers are required, which have an adverse effect on the procedure for making such belts continuous and on the intrinsic energy consumption and the production costs of the belt.
DE-A-40 39 584 describes a fabric-free drive belt or conveyor belt comprising an oriented polyamide sheet as a tension layer, which is provided on at least one side with an adhesion promoter coating, on which a rubber sheet is arranged as a rubber friction layer in the form of a laminate. The adhesion promoter coating consists, for example, of a water/alcohol-based solution containing at least 15% by weight, preferably 50% by weight, of resorcinol, and is intended to ensure that the adhesive strength requirements are met.
This fabric-free belt has the disadvantage that an adhesion promoter coating first has to be applied to the polyamide sheet and drying then carried out in order to produce the bond between the oriented polyamide sheet and the rubber sheet. Only thereafter is the bond formed under pressure and at a temperature between 140.degree. C. and 190.degree. C. Owing to the complex process engineering, however, it is difficult to achieve uniform adhesion. Consequently, this solution has not become established in the market.
DE-A-21 14 746 describes a process for the production of a flexible laminated material usable in a conveyor belt, in which a layer of an elastomeric material, which contains resorcinol and a compound becoming a methylene donator when heated, is applied to a polyamide film and subsequently the structure is heated. The resorcinol as well as the methylene donator are necessary to cause an adherence between the elastomeric material and the polyamide. Moreover, this process is not, without further difficulty applicable to an oriented polyamide layer because of its surface polarity, thereby rendering a wetting more difficult.